ISSN:
1573-2932
Source:
Springer Online Journal Archives 1860-2000
Topics:
Energy, Environment Protection, Nuclear Power Engineering
Notes:
Abstract A temporary decline in tree growth has often been observed after liming in coniferous forests poor in N but seldom in forests rich in N. To test the hypothesis that the decline was caused by decreases in N supply, C and N mineralization were estimated in incubated soil: (1) after liming in the laboratory, and (2) after earlier liming in the field. Liming increased the C mineralization rate in needle litter, nor humus and 0 to 5 cm mineral soil for a period of 40 to 100 days at 15°C. After that period, liming had no effect on the CO2 evolution rate in materials poor in N (C:N ratios 30 to 62) but increased the CO2 evolution rate in materials rich in N (C:N ratios 24 to 28). When liming induced nitrification, the CO2 evolution rate was reduced. Liming resulted in lower net N mineralization rate in needle litter and mor humus. The reduction was more pronounced when NH4 + was the only inorganic form than when NO3 − was the predominant form. The reason is probably that chemical fixation of NH3 and amino compounds increases with increasing pH. Because of the fixation, the incubation technique most likely underestimated the mineralized N available to the roots. Taking this underestimation into consideration, liming initially reduced the N release in the litter layer. In the other soil layers, liming increased the N release in soils rich in N and had only small effects in soils poor in N. For the total N supply to the roots in the litter, humus and 0 to 5 cm mineral soil layers, liming caused a slight reduction in soils poor in N and a slight increase in soils rich in N. Data on tree growth corresponded with these results.The hypotheses that tree growth depressions can be caused by reduced N supply after liming and that tree growth increases can be caused by increased N supply after liming thus seem reasonable.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00298678
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